The present invention relates to a method for braking a moving thread-like material, more especially in textile machines, and a novel thread brake device for carrying out said method.
In the hitherto known thread brakes and thread braking methods, for example in accordance with the DE OS 31 48 151 assigned to LOEPFE BROTHERS LIMITED, the moving thread or thread-like material is braked with a clamping effect and is guided between a fixed and a movable brake shoe, where the movable brake shoe is actuated by an electro-magnet controlled by a brake-thread control device so as to press the thread against the fixed brake shoe, thus clamping the thread between them. A somewhat resilient steel band has also been proposed for use as the fixed brake shoe. For releasing the thread brake when the electro-magnet does not carry current, there is employed a spring as return means, which brings back the movable brake shoe into its rest or starting position.
A thread brake of this kind, based on the principle of clamping and having such a structure has substantial disadvantages which, especially in the case of polypropylene or jute threads, lead to operational breakdowns in a very short time. For example, in the case of polypropylene thread material, the steel bands used as fixed brake shoes were destroyed in the matter of a few working shifts. In addition, after only a relatively few hours of operation, due to the erosion of fibre components and fibre-finishing substances, walls of detritus built up beside the thread track the, against which the brake shoes came to bear without effectively braking the thread. This leads to loose warp threads and thus to fabric defects. The damage which is particularly great is due to the circumstance whereby a wrongly or not inserted thread destroys the production of a large number of meters, up to 100 m, of defect-free fabric and thus a single, wrongly fed-in thread can destroy a large quantity of the product and waste a large number of working hours, because the short pieces of fabric thus produced often cannot be further processed to an equivalent extent. These losses add to the change-over losses, but in general are much larger than these. To this must also be added the material costs and the very high costs of production storage. Furthermore, the very high switching frequencies, due to the increasingly high operating speeds of the textile machines, cannot be attained with the known thread brakes. With these thread brakes, at the speeds now currently worked, the thread cannot be braked at the correct instant and with such accuracy as to produce defect-free fabrics.
The task underlying the invention is one of providing a method and a thread brake for the braking of moving threads, especially in textile machines, by means of which even very hard and fibrous threads can be braked reliably and precisely relative to the intended use of the thread, in short braking times and at higher switching frequencies and number of connections than hitherto, and that a self-cleaning effect occurs or soiling has no appreciable effect on the effectiveness of the braking. In addition, the high underlying disturbance level is to be reduced and its influence diminished.
Accordingly it is a principle object of the present invention to provide a method for braking a moving thread-like material and an apparatus for carrying out said method which overcomes the aforesaid disadvantages.